This invention relates to a curable organopolysiloxane composition and more particularly to a curable organopolysiloxane composition that exhibits excellent curability. The present invention also relates to a product formed from the organopolysiloxane composition and to a unified article.
Addition-curing organopolysiloxane compositions (abbreviated below as ACO compositions) typically comprise an alkenyl-functional organopolysiloxane and an organohydrogenpolysiloxane and cure in the presence of a platinum catalyst. These compositions are used in a variety of industrial and commercial sectors. However, their cured products have an inert surface that also exhibits release properties and, consequently, these cured products have very poor adhesion to thermosetting organic resins such as phenolic resins, epoxy resins, melamine resins, urea resins, polyurethane resins, and polyimide resins. In one method proposed for the formation of composites from thermosetting organic resins and ACO compositions, the surface of the cured ACO composition is treated with ozone and the organic resin is brought into contact with the treated surface and cured (Japanese Laid Open (Kokai or Unexamined) Patent Application Number Hei 2-27756 (27,756/1990)). However, this method has not proven satisfactory because the adhesion between the organic resin and cured ACO declines with the passage of time.
In order to solve this problem, the present inventors have previously proposed a curable composition comprising an alkenyl-functional organopolysiloxane, an organohydrogensiloxane, a hydroxyphenyl group-containing methacryl-functional siloxane, and a hydrosilylation catalyst (Japanese Patent Application Number Hei 10-278538 (278,538/1998)). Unfortunately, when this curable composition is applied and cured on the surfaces of various substrates, very small amounts of the silicone component out-migrate or effuse from the periphery of the composition prior to and during its cure. One problem associated with this effusion is that the out-migrated fraction does not adhere to substrates. Another problem occurs when such a composition is used as the base of a silicone system adhesive that is employed for bonding semiconductor chips to their substrate or package. In this case, the very small amount of silicone component that spreads out from the silicone system adhesive prior to its thermosetting will bleed out at the periphery of the semiconductor chip, resulting in contamination of the surface of the semiconductor chip, substrate, package, lead frame, and so forth. This contamination results in problems such as a decrease in wire bondability and the generation of bonding defects with the sealant resin, which can lead to reduced moisture resistance.
As a result, there is a need for a curable organopolysiloxane composition wherein the silicone component that out-migrates by effusion from the composition is also highly curable and adherent to a variety of substrates.
In another vein, ACO compositions comprising a hydrosilylation catalyst and an organopolysiloxane containing both SiH and alkenyl groups in the same molecule are known (Granted Japanese Patent 2,519,563 and Japanese Laid Open (Kokai or Unexamined) Patent Application Number Hei 1-213363 (213,363/1989)). The cured products afforded by the thermosetting of these compositions are reported to contain less uncured material than the cured products from compositions comprising an alkenyl-functional organopolysiloxane and an organohydrogensiloxane. However, due to their low SiH/alkenyl molar ratio, these compositions can only be cured to give gelsxe2x80x94which cannot be used for bonding applications due to their very low physical strength.
The present inventors have discovered that an organopolysiloxane composition comprising an organopolysiloxane containing both silicon-bonded hydrogen atoms (SiH) and alkenyl groups in the same molecule has excellent curability. In particular, the silicone component that out-migrates from the organopolysiloxane composition by effusion has excellent curablility. Also, the organopolysiloxane composition contains a compound having both alkenyl and hydroxyphenyl groups as an adhesion promoter and has excellent adhesion to a wide variety of substrates.
In specific terms, it is an object of this invention to provide a curable organopolysiloxane composition that cures rapidly on the surface of a variety of substrates. It is also an object of this invention to provide a curable organopolysiloxane composition wherein the silicone fraction that outmigrates by effusion from the composition prior to and during cure is also highly curable and adherent to a variety of substrates. Another object of this invention is to provide products afforded by curing the aforesaid composition. A further object of this invention is to provide articles in which said cured product and a substrate are unified into a single body (unified articles).
The present invention is directed to a curable organopolysiloxane composition, comprising:
(A) an organopolysiloxane containing an average of at least 2 alkenyl groups and at least 2 silicon-bonded hydrogen atoms per molecule;
(B) a compound containing alkenyl and hydroxyphenyl groups in each molecule, and
(C) a hydrosilylation catalyst.
The present invention is also directed to a product formed by curing the aforementioned organopolysiloxane composition.
The present invention is further directed to a unified article comprising a substrate and a product formed by curing the above organopolysiloxane, wherein the substrate is unified into a single integral body with the cured product.
A characteristic feature of the curable organopolysiloxane composition of this invention is that the very small amount of silicone component that effuses from the composition also undergoes a thorough cure when the composition coated on the substrate surface is heated. This results in the production of a unified article in which the cured product is solidly bonded with the substrate. This characteristic feature makes the composition of this invention well suited for use as, for example, a silicone system adhesive.
The curable organopolysiloxane composition of this invention, because it comprises the components (A), (B), and (C) as described hereinabove, is characterized by an excellent curability, and in particular the silicone component that out-migrates in a very small amount by effusion from the composition prior to and during its cure is also highly curable and produces a cured product that can tightly adhere to a variety of substrates.
These and other features, aspects, and advantages of the present invention will become better understood with reference to the following description, appended claims, and accompanying drawing.